JP2849166B2 - Pneumatic radial tire suitable for high-speed driving - Google Patents

Description

[Detailed description of the invention] (Industrial application field) In recent years, technological innovation of passenger cars has enabled stable traveling at an ultra-high speed of 200 to 300 km / h. For example, a flat radial tire having an aspect ratio (a ratio of a sectional height to a maximum width of the tire) of about 0.30 to 0.65 having sufficient performance has been developed.

The present invention relates to an improvement in a tread of a pneumatic radial tire for a passenger car, particularly a flat radial tire used for high-speed running.

(Prior Art) Many tread patterns applied to this type of tire particularly emphasize drainage and steering stability. A typical tread pattern is a pair of circumferential grooves forming a pair on both sides of the equator of the tire. While the ribs are defined, a lateral groove extending from the tread end toward these circumferential grooves in a direction inclined toward the equator of the tire is provided, and the grounding of the same lateral groove during load rolling from the center of the tread to the outside. A so-called directional pattern that is performed in order is known.

(Problems to be Solved by the Invention) The tread thickness of this kind of tire is thin in the circumferential groove, while it is thick in the land portion defined by the circumferential groove, and the mass difference between the circumferential groove and the land portion is large. In addition, the amount of outward projection in the tire radial direction due to the centrifugal force generated during ultrahigh-speed running also differs greatly. In other words, while the amount of protrusion in the circumferential groove is small, the amount of protrusion in the land is large, and especially the amount of protrusion in the rib at the center of the tread is larger than in other land parts. Becomes uneven. This impairs steering stability at ultra-high speed running and causes uneven wear.If ultra-high speed running continues, heat due to excessive contact pressure is generated especially at the center rib of the tread, and this heat is generated by the tread rubber. If the heat resistance limit is exceeded, blowout will occur, and the high-speed durability of the tire will decrease.

Therefore, the present invention seeks to provide a pneumatic radial tire having improved high-speed durability without sacrificing steering stability and uneven wear resistance, and thus having high performance that can withstand use at ultra-high speed traveling. Is what you do.

(Means for Solving the Problems) In the present invention, a belt layer and a tread are sequentially arranged radially outward of a tire on a crown portion of a radial carcass extending in a toroidal shape between a pair of beads, and the tread is provided on a tire. At least one pair of circumferential grooves extending along the equator of the tire and forming a pair on both sides of the equator of the tire, and a central land portion and a tire shaft defined by the circumferential grooves and extending continuously on the equator of the tire. A pneumatic radial tire having side land portions partitioned outward in the direction, and in a state filled with a normal internal pressure after being mounted on a normal rim, the central land portion of the tread is at least in the tire axial direction of the land portion. The center is located at a position separated by 0.1 to 1.5 mm radially inward of the tire with respect to an imaginary line of the contour of the tread that straddles the central land portion and connects each side land portion on both sides thereof. Especially A pneumatic radial tire suitable for high speed running to.

FIG. 1 (a) shows a main part of a tread of a pneumatic radial tire according to the present invention, and the tread is substantially attached to the equator (circumference at the center of the width of the tread) O of the tire.
Circumferential grooves 1a, 1b and 2a,
2b and a large number of lateral grooves 3a, 3b, 4a, 4b and 5a, 5b which connect the tread end T and the respective circumferential grooves completely or partially, and extend in a direction converging on the equator O. , Near the tread end T, two vertical column blocks 6 on each side
a, 6b and 7a, 7b and a rib 8 forming a central land portion of the tread. A tire having such a directional pattern is used by being mounted on a vehicle such that the direction in which the lateral grooves converge and the direction of rotation are matched.

It is important that the central land portion be a rib extending continuously on the equator O, particularly for suppressing the pattern noise of the tire and improving the straightness. However, as long as the object of the present invention is not impaired, it is possible to form a narrow groove or a shallow groove in the center of the rib, or to introduce cuts from the peripheral grooves on both sides, as needed, to further improve drainage properties. is there.

In the illustrated example, the number of the circumferential grooves is two on one side and four on the one side, but the number of the circumferential grooves can be arranged in the range of 2 to 4 on one side. Also, the circumferential grooves 2a and 2b are different from the straight circumferential grooves 1a and 1b. The groove width is gradually increased (decreased) according to the pitch of each block to improve the wear resistance of the blocks 7a and 7b during high-speed cornering. I am wearing it.

The angle of the transverse groove with respect to the equator O is 75 to 8 in the transverse grooves 3a and 3b.
It is preferable that the 5 ° and the lateral grooves 4a, 4b and 5a, 5b be converged at an angle of 60 to 70 ° and smaller than the former area. The groove width can be gradually increased from the equator O toward the tread end T, and the groove depth can be equal to or less than the main groove. In addition, as shown in FIG. 1 (a), the lateral grooves 5a, 5b are shown as a type that does not open to the peripheral grooves 1a, 1b side, and all the grooves penetrate between the peripheral grooves 1a, 1b and 2a, 2b. You don't have to.

Next, FIG. 2B illustrates the structure of the tire according to the present invention.

In the drawing, reference numeral 9 denotes a carcass stretched in a toroidal shape between a pair of beads (not shown), reference numeral 10 denotes a belt layer disposed on the carcass 9, and reference numeral 11 denotes a tread disposed on the belt layer 9.

The carcass 9 comprises at least one layer (usually one or two) of layers in which organic fiber cords represented by polyester, rayon and nylon are arranged in a direction (radial direction) substantially perpendicular to the equatorial plane of the tire, Both ends of the carcass layer (ply) are wound around the bead core from the inside to the outside of the tire to form a turn-up ply.

The belt layer 10 is formed of at least two belts in which non-extensible cords such as steel cords and aromatic polyamide fiber cords are arranged at an angle of 15 to 35 ° with respect to the equatorial plane of the tire.
A main belt layer 10a in which the layers are arranged crossing each other,
An auxiliary belt layer 10b in which one or a plurality of heat-shrinkable cords with rubber (for example, nylon cords) are spirally wound around the entire width of the main belt layer 10a and arranged substantially parallel to the equatorial plane of the tire. . Then, the tread 11 is arranged on the belt layer 10.

In forming the above-described tread pattern on the surface of the tread 11, the surface of the rib 8 is positioned radially inward of the other land portions, that is, the surfaces of the column block groups 6a, 6b and 7a, 7b.

That is, the surface of the rib 8 crosses the rib 8 and connects the vertical block groups 7a and 7b on both sides of the rib 8.
On the other hand, the ribs 8 are formed so as to be spaced radially inward of the tire by a distance h within a range of 0.1 to 1.5 mm.

Although FIG. 2B shows a tread structure in which the entire surface of the rib 8 is separated from the outline virtual line L in the above range, the center of the rib 8 in the tire axial direction is set as shown in FIG. The intended purpose can be satisfied also by forming a structure in which a depression is formed at the center of the rib 8 at a distance from the contour virtual line L in the range of.

(Operation) The heat generated in the central land of the tread during high-speed driving is more intense than the heat generated in the land on both sides of the central land, causing early blow-out and reducing high-speed durability. The present inventors have investigated the cause of the particularly strong heat generation in the central land portion, and found that the central land portion has a larger rubber mass than the other land portions, a large amount of protrusion due to centrifugal force, and a low heat radiation ability. And so on. Therefore, focusing on the contact pressure in the central land area, it has been found that the above problem can be solved by reducing the contact pressure.

That is, the contour imaginary line L described above is the center land portion of the tread.
By separating the tire radially inward,
The central land portion was designed to be in contact with the ground only when the tire is rolling. Therefore, heat generation can be suppressed by reducing the amount of protrusion due to the rubber mass and the centrifugal force while securing the straight running property and uneven wear resistance during running, so that high-speed durability can be improved.

Here, the central land portion is at least the center in the tire axial direction,
It is advantageous that the tread contour virtual line L is separated radially inward of the tire by 0.1 to 1.5 mm. If the distance is less than 0.1 mm, the amount of protrusion at high speeds exceeds 0.1 mm, so that at 150 km / h or more, the surface pressure on the central land will eventually increase. On the other hand, if it exceeds 1.5 mm, the level difference from the land part at the time of normal driving becomes large, causing uneven wear.

(Example) Tire size according to the tread pattern shown in FIG. 1A and the structure shown in FIG. 1B or FIG.
Two types of 255 / 40ZR17 pneumatic radial tires (test tires A and B) were prototyped.

In these test tires, the circumferential grooves 1a and 1b have a width of 10 mm and a depth of 8.5 mm, the circumferential grooves 2a and 2b have a maximum width of 10 mm, a minimum width of 8 mm and a depth of 8 mm, and the lateral grooves have a width of 5 mm and Depth: 7mm, converged at 30 ° to the equator of the tire, circumferential grooves 2a, 2b near the tread edge
The angle between the horizontal grooves was 10 °, and the angle between the circumferential grooves 1a, 1b at the center of the tread and the horizontal grooves was 30 °.

The width of the rib 8 is 15mm, and the contact width of the tread is 20
0 mm. Then, the surface of the rib 8 of the test tire A is flattened and the entire surface is separated from the contour virtual line L of the tread by h = 0.3 mm, while the surface of the rib 8 of the test tire B has a radius of curvature of 10,000 mm outward in the tire radial direction. The center of the tire in the axial direction is separated from the imaginary line L of the tread by h = 0.2 mm. In addition, the surface of the other land portion (the group of tandem blocks) of the rib 8 was formed to have a convex cross-section having a radius of curvature of 6000 mm outward in the tire radial direction.

On the outside of the carcass, a main belt layer in which two layers of 1 × 5 steel cords arranged at an angle of 20 ° with respect to the equator of the tire are arranged to cross each other, and the entire width of the main belt layer is a nylon cord (1260 d / 2) and an auxiliary belt layer.

For comparison, the structure shown in FIGS. 1 (a) and 1 (b) is followed, but the ribs 8 have the same size for the tire on the imaginary line L of the tread as the surface of the other land portion (group of tandem blocks). Prototyped with

The results of evaluation of these prototype tires in a steering stability test, a high-speed durability test, and an uneven wear resistance test are shown in the following table.

The test was conducted using a normal car with one driver on board.
And expressed as an index.

In the driving stability test, the driver evaluated the feeling of straightness and lane changeability when traveling at 100 to 200 km / h, and in the high-speed durability test, the internal pressure was 2.5 kg / cm on a 2 m diameter drum.
^With the tire set as ² , pressed with a load of 500 kg, 150 k
From 10 m / h to 10 km / h speed increase every 10 minutes until failure occurs, evaluation at the speed at the time of failure, uneven wear resistance test was performed on a circular test course with a radius of 400 m
The vehicle was turned at km / h and evaluated based on the wear pattern after traveling 100 km.

(Effects of the Invention) According to the present invention, there is provided a high-performance tire capable of improving high-speed durability without sacrificing steering stability and uneven wear resistance, and capable of withstanding running in an ultra-high speed range. Becomes possible.

[Brief description of the drawings]

FIG. 1 (a) is a developed view of a tread pattern according to the present invention, and FIG. 1 (b) shows a tread structure, taken along the line II in FIG. 1 (a).
FIG. 2 is a sectional view showing the structure of another tread. T: tread edge, O: equator of the tire L: virtual tread contour line 1a, 1b, 2a, 2b ... circumferential groove 3a, 3b, 4a, 4b, 5a, 5b ... lateral groove 6a, 6b, 7a , 7b ...... tandem block group 8 ... rib, 9 ... carcass 10 ... belt layer, 10a ... main belt layer 10b ... auxiliary belt layer, 11 ... tread

Claims (1)

(57) [Claims] 1. A belt layer and a tread are sequentially disposed radially outward of a tire on a crown portion of a radial carcass extending in a toroidal shape between a pair of beads, and the tread extends along an equator of the tire and has a tire. At least one pair of circumferential grooves forming a pair on both sides of the equator, a central land portion defined between the circumferential grooves and continuously extending on the equator of the tire, and sides defined on the outer side in the tire axial direction of the circumferential grooves. A pneumatic radial tire having a land portion, and in a state where a normal internal pressure is applied after being mounted on a normal rim, a center land portion of the tread has at least a center of the land portion in the tire axial direction and a center land portion thereof. Suitable for high-speed running characterized in that it is located at a distance of 0.1 to 1.5 mm radially inward of the tire with respect to the imaginary line of the tread that connects each side land part on both sides by straddling it Inflated Radial tires.